Shape and spin-state model of asteroid (99942) Apophis reconstructed from photometric observations in 2020/21

<p>(99942) Apophis is a near-Earth asteroid that will closely approach to Earth in 2029; the minimum geocentric distance will be about 38,000 km.&#160; During the approach, the spin state of Apophis is expected to be altered by Earth's gravitation torque.&#160; The exact change depends on the orientation of Apophis during the close approach.&#160; Although the shape and spin-state model of Apophis was reconstructed from 2012/13 observations by Pravec et al. (2014, Icarus 233, 48),&#160; the precision of rotation parameters they derived was not sufficient to predict the orientation for 2029. <br /><br />We will present our analysis of photometric observations of Apophis that we carried out from 2020-11-16 to 2021-05-06 with the 1.54-m Danish telescope at La Silla.&#160; By applying the lightcurve inversion technique of Kaasalainen (2001, A&A 376, 302), we reconstructed the spin state and shape of Apophis.&#160; This new model agrees with the one reconstructed by Pravec et al. (2014) and with an updated model published by Lee et al. (2022, arXiv:2204.02540).&#160; We aimed to invert both the 2012-2013 and 2020-2021 data together and reconstruct the Apophis spin state with high precision.&#160; The long interval of observations would enable us to precisely determine the rotation and precession periods and thus reliably predict&#160; the orientation of Apophis during its 2029 flyby, calculate a change of its spin state, and predict how the Yarkovsky effect will influence&#160; the post-encounter orbit of Apophis, which is crucial for its post-2029 impact predictions. <br /><br /><br /></p>